The present invention relates to a thermostat valve used in a cooling system of an automobile, more particularly, to an adjustable electronic thermostat valve.
In general, a thermostat valve is installed between the automobile engine and radiator and functions to maintain the temperature of coolant in a preferred range by controlling the flow of coolant to the engine in accordance with change of the temperature of the coolant. The thermostat valve can eventually control the temperature of the engine by control of the amount of flow of the coolant.
A conventional thermostat valve that is widely used is a mechanical operating type that opens or closes the valve in accordance with up and down movement of a piston through which the expansion and contraction of a thermal expandable element is transferred. For example a thermostat of the mechanical operating type may include a wax activator. When the temperature of the coolant rises above a threshold value (approximately 80xcx9c90xc2x0 C.), the wax in a solid state is changed into liquid. Subsequently, the actuating force generated by the expansion of the volume of the wax is transferred to a valve mechanism.
However, the above-described conventional thermostat valve is disadvantageous in that there is a limit to the ability to control the temperature of the coolant considering, for example, driving conditions because the opening and closing operation of the valve only depends on the preset temperature of the coolant. While a cooling system of an automobile is generally designed to satisfy the toughest driving condition such as full load, high ambient temperature, and etc., actual driving is, however, typically conducted with about 70% of full load. Accordingly, overcooling of the engine can occur, which results in increasing consumption of fuel and exhaust containing excessive pollutants.
For the foregoing reason, there is a need for a thermostat valve that can optimize a temperature of coolant to engine by raising the temperature of a coolant while the engine is operating with partial load and lowering the temperature of a coolant while the engine is operating with full road. In order to overcome drawbacks of the prior art, attempts to provide an adjustable electronic thermostat valve that optimizes a temperature of coolant to engine have been made. Ideally, such an adjustable electronic thermostat valve would maintain an engine under the optimized cooling condition by controlling the temperature of coolant to the engine based on driving conditions and load conditions, whereby decrease of exhaust gas and fuel consumption can be expected.
In prior attempts to address this problem, thermostat valves have been provided with heating means to cooperate with the expandable wax element. Such an electronic thermostat valve comprises basically same elements as a conventional mechanical thermostat valve with the addition of the heating means. Power supplied to the heater is controlled based on driving conditions such as speed of an automobile, temperature of intake air, and loading conditions.
However, the above-described electronic thermostat valve is disadvantageous in that the parts of the valve are relatively easily damaged by high temperature caused by heating means, and further, the response time is slow. The specific drawbacks of prior electronic thermostat valves include, for example, heating defects created in the wax or other elements of the valve, and delay in operating the valve in response to the supply electric power to the heater because of the time delay to heat up the heater and expand the wax. Also, in the process of sealing the thermostat valve case, electric wires for supplying electric power to the heater can be damaged. Even if the sealing process is completed without any defect in the electric wires, the sealing material such as epoxy is easily degraded or destroyed due to the vibration of a engine. In the event that the thermostat valve is operated in safe-mode due to the failure of electronic parts, the engine continues to overheat potentially resulting in critical damage to the engine.
Embodiments of the present invention provide an adjustable electronic thermostat valve comprising an actuating means provided with a rod for stroking a chamber of an expendable thermal element. With this arrangement, the temperature at which the thermostat valve opens and closes, can be easily adjusted based on driving conditions by changing the volume of the chamber of the expendable thermal element, whereby a cooling efficiency of the engine is maintained in optimized range. As a result, emission of exhaust gas and consumption of fuel is significantly reduced.
Further, preferred embodiments of the present invention include actuating means capable of directly changing the volume of the chamber of the expendable thermal element, so that the operation of the valve in response to a control signal is promptly accomplished. This can provide a rapid response characteristic, whereby temperature of coolant to an engine can be accurately controlled.
Also, a fail-safe device is preferably included so that the thermostat valve properly functions with only the expandable thermal element operating when the actuating means of the valve is unable to operate due to the failure of supplying electric power.
Preferably an adjustable electronic thermostat valve according to the invention comprised an actuating means employing a screw-feeding method to obtain sufficient displacement of the valve even though the stroke of the actuating means is relatively small.
Also, preferred embodiments unintended movement of the valve such as a fluctuation or vibration by fixing the expandable thermal element of the valve, whereby the valve is more accurately opened or closed.
An adjustable electronic thermostat valve according to further preferred embodiments of the present invention comprises an actuating means that operates in response to control signals concerning driving conditions, with the actuating means having a screw-feeding rod. A chamber accommodating an expandable thermal element begins to expand at preset temperature wherein the volume of the chamber is changed by the screw-feeding rod. A piston is operatively connected to the chamber and opens or closes a valve plate in accordance with the change of volume of the chamber. A power-delivering liquid and diaphragm transfers expansion force of the expandable element to the piston.